The invention relates to a configuration of a plurality of circuit modules disposed essentially one above the other approximately in the form of a stack. A respective connecting device is provided for the external electrical bonding of the circuit modules. An electrical connection is at least partially provided between the connecting devices of the circuit modules, and an electrical connection of various connecting devices among one another is respectively formed by essentially direct mechanical and electrical contact of various connecting devices.
In circuit engineering, and, in particular, in semiconductor electronics, it has for some time been endeavored to construct circuit configurations that realize as high a number of components and/or circuit functions as possible in the smallest space. It is accordingly endeavored to keep reducing the size of the corresponding components and circuit functions within the bounds of physical possibilities. Because, in the endeavor, it is not possible to go below certain physical limits, it must be expected that, for each electronic component, there will be a minimum size, based on physical principles, but, under certain circumstances, the minimum size can only be realized in mass production with considerable expenditure in terms of cost.
Ways around the dilemma, ensuring the highest possible utilization of the surface area by corresponding wiring, have accordingly been sought. For instance, it has been proposed, in particular, in the case of semiconductor modules, to dispose chips, or quite generally in the case of circuit modules, to position a plurality of the necessary circuit modules such that they are disposed in layers one above the other in the vertical direction. The stacking, as it is known, of a plurality of circuit modules consequently departs from the two-dimensional plane and package and makes it possible to utilize the third dimension, in the vertical direction, by corresponding packing of a plurality of circuit modules one above the other.
It is often necessary for the circuit modules disposed one above the other to be interconnected. Thus, the connecting devices necessary in each case for the external electrical bonding of the respective circuit modules must also be at least partially electrically and electronically connected to one another by a plurality of connecting elements, i.e., the initially electrically isolated circuit modules must be interconnected by connecting devices that have to be provided. Various concepts for the interconnection have been proposed to interconnect the connecting devices of the respective circuit modules.
The prior art includes, for example, a positioning of circuit modules of various sizes one above the other so that a frustopyramidal structure of circuit modules decreasing in their base area in the vertical direction from the bottom upward is produced and is then disposed as a stack on a corresponding carrier. For interconnection, corresponding wire bonds are then individually led down from each circuit module onto the surface of the common carrier, where the actual electrical bonding with the outside and among the modules is then realized on a corresponding conductive substrate. One disadvantage of such a procedure is that circuit modules of different sizes, i.e., base areas, have to be configured, resulting in a problematical combination of identical modules. Another disadvantage is that respective individual wire bonds have to be formed and pulled, which, although it does not preclude automation of the bonding, makes such an automatic process difficult.
If, on the other hand, circuit modules of an identical size are stacked one above the other, the interconnection of the circuit modules lying at the top by corresponding wire bonds is necessary even if the circuit module disposed at the very bottom can be attached and bonded on the common carrier, for example, by flip-chip technology.
To circumvent such problems, other procedures have also been proposed. For example, U.S. Pat. No. 5,016,138 to Woodman discloses a configuration of a plurality of circuit modules in which the circuit modules are disposed essentially one above the other, for instance, in a stack. For the external bonding of the circuit modules, in each case a connecting device with a plurality of connecting elements is provided. In the prior art according to U.S. Pat. No. 5,016,138, the connecting device is realized by respectively disposing the individual chips on a separate carrier, on which the contacts of the chips are then led out through a printed-on circuit configuration to the margin of the carrier, to corresponding contact pins that are disposed in the edge region of the carrier. The respective entireties of contact pins are then electrically bonded and interconnected by a plurality of bonding and interconnecting plates reaching laterally around the stack.
A disadvantage of such a procedure is that each circuit module must, in turn, be placed on a carrier and that the interconnection of the various carriers necessitates the assembly of a multiplicity of individual components because an inherent interconnection of modules is not possible here on account of their natural construction.
It is accordingly an object of the invention to provide a configuration of a plurality of circuit modules that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that interconnects the circuit modules disposed one above the other in a particularly reliable and, nevertheless, simple and low-cost way.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a circuit configuration, including a connection carrier, circuit modules disposed essentially one above another approximately in a stack, each of the circuit modules having a connecting device for externally and electrically bonding the circuit modules, the connecting device having at least one series configuration of connecting elements disposed essentially in a plane, the connecting elements disposed on the connection carrier, and the connecting device of at least one of the circuit modules at least partially electrically connected to another connecting device of at least one different one of the circuit modules in direct mechanical and electrical contact.
In the congeneric configuration of a plurality of circuit modules, the circuit modules are disposed essentially one above the other approximately in the form of a stack. For the external electrical bonding of the circuit modules, in each case a connecting device with a plurality of connecting elements is provided. An electrical connection is at least partially provided between the connecting devices of the circuit modules.
The configuration according to the invention of a plurality of circuit modules is characterized in that an electrical connection of various connecting devices among one another is respectively formed by essentially direct mechanical and electrical contact between connecting elements of various connecting devices.
It is consequently a basic idea of the invention to achieve an electrical contact, and, consequently, an interconnection, of the circuit modules in the configuration of a plurality of circuit modules by the connecting elements of the circuit modules, each of which in themselves form a corresponding connecting device of the circuit module for external electrical bonding. The connecting elements are connected essentially directly to one another and without further bonding devices being interposed or used. If, consequently, circuit modules disposed one above the other have to be interconnected, such interconnection takes place according to the invention by configuring the connecting elements that form the connecting devices of the respective circuit modules such that they can enter essentially directly into contact with one another. The directness is not precluded by a soldering or welding flux being provided for the electrical bonding and fixing.
In principle, such a configuration according to the invention requires no additional components for the electrical bonding of the circuit modules disposed one above the other for establishing the contact between the individual connecting elements of the circuit modules. As a result, assembly is made more simple and reliable.
The configuration according to the invention of a plurality of circuit modules is made particularly advantageous if the connecting elements have the same form or have essentially the same effect with regard to their geometrical, mechanical and/or electrical properties. Specifically when essentially coinciding circuit modules are used, it is appropriate for all the connecting elements that form the connecting device of the respective circuit modules to be identically configured, which allows for a mass production process.
In accordance with another feature of the invention, the connecting elements are fixed on the connection carrier.
The connecting elements are preferably configured as a connecting wire, which is formed, in particular, with an essentially linear extent. With such a connecting element in the form of a connecting wire, all the distances, for example from a contact region on any face of the circuit module to its margin, can be bridged in a simple way. In addition, connecting wires have particularly favorable properties with regard to their dimensional stability and mechanical durability. They are simple to produce, can be easily shaped, and are, nevertheless, resistant enough to be used in an automatic assembly and component-insertion machine.
In accordance with a further feature of the invention, the connecting elements, in particular, the connecting wires, each have a first end for the electrical bonding to a respective circuit module. Furthermore, a second end is provided, which may serve if appropriate for the electrical bonding to at least one other connecting element of another circuit module. Furthermore, the connecting element, in particular, the connecting wire, has a main region, which extends between the first end and the second end of the connecting element and which covers, in particular, the distance between the regions to be bonded.
A particularly simple geometrical configuration provides that the second ends of the connecting elements, in particular, the connecting wires, each have a region extending essentially linearly and/or essentially perpendicularly in relation to the main region. Thus, in the case of the connecting elements, the main region and the second end for the electrical bonding to other connecting elements of other circuit modules are essentially perpendicular to each other. In such a case, it is of particular advantage that the connecting elements, in particular, the connecting wires, preferably have essentially the form of a hook, in particular, an elongated hook, an xe2x80x9cLxe2x80x9d, a claw or the like. Furthermore, it is preferred in such case for a kind of shoulder or the like to be respectively formed in a transitional region between the main region of the connecting element and the first and/or second end of the connecting element.
Based upon the above measures, on one hand, a contact with the circuit module to be interconnected can be established and, on the other hand, an interconnection with vertically neighboring circuit modules can be realized in a particularly simple way. The connecting element, the shoulders, and, in particular, the second end region of the connecting elements are suitable for forming a contact with other connecting elements.
During the assembly of the configuration according to the invention of a plurality of circuit modules, permanent deformations, in particular, of the connecting elements or connecting devices, must be avoided. Because, however, during the positioning of the circuit modules provided with the connecting elements, a certain tolerance in the positioning and movement of the individual circuit modules in the vertical direction, but also in the horizontal direction, cannot be ruled out, it is of particular advantage that the connecting elements of the configuration according to the invention of a plurality of circuit modules, in particular, the connecting wires, are each flexibly resilient, in particular, in the region of the second ends. The resiliency allows the connecting elements to take up the tolerances during the positioning, and the resultant mechanical damage, without defects occurring in the connecting elements themselves or at the contact points.
A configuration according to the invention of a plurality of circuit modules is advantageously formed specifically by configuring each of the circuit modules in essentially the same form and/or to have essentially the same effect with regard to their geometrical, mechanical and/or electrical, especially electronic, properties.
Particularly space-saving configurations or stacks are obtained if a high packing density or stacking density can be achieved. Experience shows, however, that a prerequisite for a high stacking or packing density is a similarity in the geometrical and mechanical properties. In addition, it may indeed also be of advantage if the electrical properties, and, in particular, the circuit properties, are correspondingly made to match one another.
The circuit modules are preferably each configured such that they are essentially of a flat, laminar, or similar form and/or essentially planar, with an upper side and an underside in each case. Such configuration likewise permits a particularly high packing density, which can then be achieved in a simple way, in particular, within an automatic production process.
The circuit modules preferably have in each case at least one semiconductor chip, in particular, a memory device, and/or they are configured as such a device. The stacking of memory elements one above the other has the enormous advantage that the electronic similarity of essentially identical circuit modules can be utilized. Achievement of the highest possible utilization of the wiring surface area is also necessary and desirable in the case of memory devices. Such utilization can be achieved in a simple way based on the configuration according to the invention of a plurality of circuit modules.
For the electrical bonding of the circuit modules to their connecting devices, in particular, to the respective connecting elements, the circuit modules have in each case at least one contact region, which is provided, in particular, with a plurality of contacts for the external electrical bonding. In the case of semiconductor modules or chips, these contacts are generally realized by what are referred to as pads, which specifically realize the contact point of the internal semiconductor structure with the outside world. According to the invention, it is provided that the connecting elements of the connecting device of a circuit module, in particular, the first ends thereof, are electrically bonded in each case to the contacts of the contact region of the respective circuit module.
The contacts are preferably formed by metallic regions on the circuit modules, to be precise, preferably on their underside and, in particular, by pads, as they are known. In particular, in the case of memory chips, it has become established practice and is of advantage that the contact regions are in each case formed on an underside of the circuit module, in an essentially central region thereof in each case.
The industrial standard also refers to what are known as center pad chips (CPC).
In the construction of the connecting devices, certain forms of configurations have proven to be particularly advantageous. For instance, it is envisaged that the connecting device has least one series configuration of, in particular, equidistantly spaced-apart, parallel, and/or flush aligned and/or similarly oriented connecting elements, which are preferably aligned along at least one edge region of the respective circuit module. It is, thus, of particular advantage that, for example, connecting wires of the same form and length are disposed such that they are aligned parallel to one another and flushxe2x80x94in the manner of a comb.
It is preferred for the connecting device to have two series configurations of connecting elements and for the series configurations, in particular, the connecting elements thereof, to be disposed in each case such that they laterally coincide with one another or are staggered in relation to one another. The series configurations preferably lie essentially in a common plane and are disposed essentially mirror-symmetrically in relation to an axis lying in the plane.
The construction achieves the effect that the two series configurations of connecting elements are opposite each other such that the first ends respectively of the connecting elements of the series are facing one another and that the second endsxe2x80x94for the external electrical bondingxe2x80x94are in each case furthest away from one another. By such a staggered or coinciding configuration, allowance can be made for the respective configuration of the contacts on the underside of the circuit module.
The connecting elements or connecting wires form, for example, bonding legs, which in a coinciding configuration are aligned essentially in a co-linear manner. In such a case, each of the series configurations extends for example along one edge of the associated circuit module, with the result that two opposite edges remain free, while the two series configurations of connecting elements run at least partially along the two other opposite edges of the circuit module.
In another advantageous embodiment of the configuration according to the invention of a plurality of circuit modules, the connecting device has in each case four series configurations of connecting elements. These four series configurations are respectively disposed essentially along at least one edge region and lie in pairs opposite one another. The configuration achieves the effect, for example in the case of a circuit module with a square or rectangular base area, that a series of connecting elements extends in each case along an edge of the circuit module. Accordingly, a particularly high number of connecting devices can be formed.
It is also provided that the plurality of series configurations, in particular, the connecting elements thereof, lie essentially in a common plane. It is also provided that the series configurations lying respectively opposite one another, in particular, the connecting elements thereof, are aligned mirror-symmetrically in relation to an axis in the plane. The individual connecting elements of the opposite series configurations are then again aligned in a co-linear or coinciding manner or the connecting elements are staggered in relation to one another.
The series configurations can indeed be formed in each case by individual and separate connecting elements. However, the series configurations are advantageously formed in each case by an assembly of connecting elements that are disposed on a connection carrier and/or are fixed there. In such a configuration, an adhesive or adhesively bonding medium, in particular, a double-sided adhesive medium, may be formed as the connecting carrier, in particular, as a tape. The individual connecting elements are then able, in particular, to be applied and/or embedded there. Thus, a kind of double-sided adhesive tape or a corresponding embedding or adhesive bonding compound can be envisaged.
For the electrical bonding and interconnection of the circuit modules disposed one above the other, the series configurations of circuit modules provided directly one above the other have at least partially essentially vertically coinciding connecting elements. Consequently, the directly neighboring connecting elements of the circuit modules disposed directly one above the other can be brought into contact with one another in a particularly simple way to bring about an interconnection of the circuit modules.
It is of advantage that at least some of the vertically coinciding connecting elements of circuit modules provided directly one above the other are formed in such a way, in particular, with regard to their orientation, their geometrical dimensions, and/or the like, that they can be brought into mechanical and electrical contact with one another. In particular, a connecting element of a first circuit module that is disposed vertically higher in each case is to be electrically bonded by its second end in the region of a shoulder or of the second end of the respective vertically coinciding connecting element of the second circuit module disposed directly vertically thereunder.
The construction is realized in a particularly simple way, in particular, by forming the mechanical and electrical contact of the connecting elements by soldering, welding, in particular, laser welding, and/or based on a force closure with spring pretensioning in the region of the second ends of the connecting elements.
For better handling and for the electrical bonding and use of the configuration according to the invention of a plurality of circuit modules, a carrier is provided, on which is disposed, fixed, and/or electrically bonded the lowermost of the circuit modules. Advantageously a housing device is formed, in particular, in the form of a casting compound, in which at least the circuit modules can be accommodated. These measures ensure that the configuration of the plurality of circuit modules as a whole can be handled in a simple way. In such a case, the envisaged carrier may also have appropriate interconnection and electrical bonding, for example, for fitting into a higher-level device.
The configuration of circuit modules provided in the prior art has the disadvantage that compromises have to be made with regard to the circuit modules to be used, or else require a considerable expenditure for the connection of the circuit modules to one another.
In particular, by configuring what are referred to as center pad chips one above the other, in particular, in a chip scale package, these disadvantages cannot be accepted. With the configuration according to the invention of a plurality of circuit modules, these disadvantages are avoided by a fundamental connection concept applying universally to all the circuit modules disposed one above the other. The construction according to the invention makes it possible in a simple way for the electrical connections to be led out to the margin of the circuit configuration and around the circuit configuration by the respective connecting devices or connecting elements. It is, consequently, possible to produce standard individual components, that is the circuit modules, which allow themselves to be mounted and disposed one above the other, and such placement takes place in a way that is particularly simple and suitable for automation. The electrical connection is achieved in each case by the overlapping and permanent connection of the connecting elements or connecting wires (interconnector leads). The connecting wires or connecting elements may either be applied individually or else be made in the form of a structured flex tape.
It is also possible to mount more than two circuit modules or chips one above the other. In addition, there is, in principle, the possibility, in a simple way, of removing defective components from the stack of circuit modules that are disposed one above the other and are interconnected.
In accordance with an added feature of the invention, there are provided spacing elements, with respective spacing elements provided between every adjacent pair of the circuit modules.
In accordance with a concomitant feature of the invention, the spacing elements remove heat from the circuit modules, preferably, the spacing elements are heat sinks.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a configuration of a plurality of circuit modules, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.